Rare sugars are monosaccharides existing at very slight amounts in the natural kingdom. Rare sugars are grouped in aldoses, ketoses and alcohols, depending on the chemical structures. The aldoses include for example D-allose; the ketoses include for example D-psicose; and the alcohols include for example allitol.
Because most of such sugars were hardly available since the mass production thereof was not achieved, almost no research works about the physiological activities and pharmacological activities thereof were done. A method for producing the sugars at a mass scale has been developed recently by Izumori, et al., in the Agricultural Department, the National University Corporation Kagawa University, so that research works about the biological activities thereof are now under way. In vitro experiments with leukocyte, an action of suppressing active oxygen generation has been found in D-allose, while in D-psicose, an active oxygen-scavenging action and MCP-1 secretion-suppressing action have been found at similar experiments (patent reference 1).
Neuropathic pain is a pain without any stimulation of peripheral sensory receptors and is a chronic pain caused by the direct damages and pressurization of nerve tissues as induction factors. Pain induced by malignant tumor, diabetic neuralgia, herpes zoster and the like is a typical neuropathic pain. Additionally, pain occurring one to 6 months after the incidence of bone fracture, injuries, and burn is also classified as neuropathic pain. The symptoms are spontaneous pains sustaining or emerging spontaneously, involving abnormal sensations such as numbness, electric current shock, minced-up feeling and biting, hyper-sensitivity against algesthesia and allodynia. The mechanism of the occurrence is not known. As hypotheses, there are suggested for example the disorders of the blood nerve barrier, abnormal synapse formation in lumber spinal dorsal horn cells, the abnormal regeneration of demyelinated fiber, the increase of receptor sensitivity, and the abnormal distribution of sympathetic nerve fiber. Specific diseases with neuropathic pain include for example trigeminal neuralgia, postherpeutic neuralgia, pain after traumatic peripheral nerve damages, painful diabetic neuropathy, and pain after arm neuroplexus is pulled out and damaged, and additionally include for example phantom limb pain, and pains due to spinal diseases, injuries, multiple-sclerosis, syringomyelia, spinal cord tumor, and brain cancer, and still more additionally include cancer pain for which analgesic effects with narcotic analgesics such as morphine are insufficiently effective.
Therapeutic treatment (amelioration) represents the effect of suppressing pain emerging in a neuropathic fashion, through the administration of a drug after nerve damages, and also represents the effect of mitigating pain or eliminating pain by allowing the abnormalized pain threshold to be back around the normal level.
Therapeutic treatment (amelioration) represents the effect of suppressing pain emerging in a neuropathic fashion, through the administration of a drug after nerve damages, and also represents the effect of mitigating pain or eliminating pain by allowing the abnormalized pain threshold to be back around the normal level.
The countermeasure against neuropathic pain at clinical practice is insufficient, unfortunately. A therapeutic method for such diseases includes a nerve blocking therapy using local anesthesia. However, such therapeutic method is almost never effective for cases with the diseases sustained for a long period of time. Additionally, the therapeutic treatment itself should disadvantageously be continued for a prolonged period of time. Further, various analgesics have been attempted. However, almost not any effective analgesics have been developed. In recent years, meanwhile, attention has been focused on pharmaceutical therapies, so that examinations about tricyclic antidepressants (amitriptyline, imipramine, and nortriptyline), gabapentin, mexiletine, clonidine, ketamine, opioide (morphine, fentanyl) and drugs for local administration such as capsaicin are made for their actions of mitigating the pain of neuropathic pain. It has been shown that thalidomide mitigates neuropathic pain by preventing the damage of the blood nerve barrier. Therefore, an outcome in future will be expected. However, these drugs are now held at experimental stages, so some clinically verified effect cannot be expected. Further, it has been known that analgesics effective for general noniceptive pain, particularly narcotic analgesics are hardly effective for neuropathic pain. For example, morphine has a strong analgesic action for noniceptive pain but morphine is hardly effective for neuropathic pain (non-patent reference 1).    Non-patent reference 1: The Lancet 353, 1959-1966, 1999    Patent reference 1: International Patent Publication No. WO 03/097820